Maybe Alliance are the smartest guys in the room. Why fix what ain't broke? Why upgrade to a more expensive fleet, and then have to compete with all the other contenders? He with the lowest costs wins.
As far as I can see Network have a plan to replace the aging Fokkers with the ex Jetstar A320s.
But is that Network's plan, or their owners? If Network can't compete with Alliance in FIFO now with the same equipment, how will they compete with a more expensive type?
QF bought more F100's for Network (must have thought they were the right aircraft for the job). Now it is Network struggling to absorb the A320s that Qantas needs to move out of Jetstar. Alliance meanwhile sails along.